U.S. patent application number 13/039361 was filed with the patent office on 2011-09-08 for supercritical processing apparatus and supercritical processing method.
This patent application is currently assigned to TOKYO ELECTRON LIMITED. Invention is credited to Mitsuaki IWASHITA, Kazuyuki MITSUOKA, Hideo NAMATSU, Hidekazu OKAMOTO, Takayuki TOSHIMA.
Application Number | 20110214694 13/039361 |
Document ID | / |
Family ID | 44530244 |
Filed Date | 2011-09-08 |
United States Patent
Application |
20110214694 |
Kind Code |
A1 |
TOSHIMA; Takayuki ; et
al. |
September 8, 2011 |
SUPERCRITICAL PROCESSING APPARATUS AND SUPERCRITICAL PROCESSING
METHOD
Abstract
Disclosed is a supercritical processing apparatus and a
supercritical processing method for suppressing the pattern
collapse or the injection of material constituting a processing
liquid into a substrate. A processing chamber receives a substrate
subjected to a processing with supercritical fluid, and a liquid
supply unit supplies a processing liquid including a fluorine
compound to the processing chamber. A liquid discharge unit
discharges the supercritical fluid from the processing chamber, a
pyrolysis ingredient removing unit removes an ingredient
facilitating the pyrolysis of a liquid from the processing chamber
or from the liquid supplied from the liquid supply unit, and a to
heating unit heats the processing liquid including a fluorine
compound of hydrofluoro ether or hydrofluoro carbon.
Inventors: |
TOSHIMA; Takayuki;
(Kumamoto, JP) ; IWASHITA; Mitsuaki; (Yamanashi,
JP) ; MITSUOKA; Kazuyuki; (Yamanashi, JP) ;
OKAMOTO; Hidekazu; (Tokyo, JP) ; NAMATSU; Hideo;
(Tokyo, JP) |
Assignee: |
TOKYO ELECTRON LIMITED
Tokyo
JP
|
Family ID: |
44530244 |
Appl. No.: |
13/039361 |
Filed: |
March 3, 2011 |
Current U.S.
Class: |
134/21 ;
156/345.37 |
Current CPC
Class: |
B08B 5/00 20130101; B08B
13/00 20130101 |
Class at
Publication: |
134/21 ;
156/345.37 |
International
Class: |
B08B 5/00 20060101
B08B005/00; B08B 13/00 20060101 B08B013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 5, 2010 |
JP |
2010-049567 |
Claims
1. A supercritical processing apparatus, comprising: a sealable
processing chamber in which a processing is performed on a
substrate with a supercritical fluid; a liquid supply unit
configured to supply a processing liquid including a fluorine
compound to the processing chamber; a liquid discharge unit
configured to discharge the supercritical fluid from the processing
chamber; to a pyrolysis ingredient removing unit configured to
remove an ingredient facilitating pyrolysis of liquid supplied from
the processing chamber or from the liquid supply unit; and a
heating unit to heat the liquid supplied to the processing chamber,
wherein the fluorine compound is hydrofluoro ether or hydrofluoro
carbon.
2. The supercritical processing apparatus as claimed in claim 1,
wherein the pyrolysis ingredient removing unit comprises a bubbling
unit configured to supply inert gas to a processing liquid before
the processing liquid is supplied from the liquid supply unit and
to perform a bubbling process.
3. The supercritical processing apparatus as claimed in claim 1,
wherein the pyrolysis ingredient removing unit comprises a first
gas supply unit to supply an inert gas to the processing
chamber.
4. The supercritical processing apparatus as claimed in claim 3,
further comprising a controller to control the pyrolysis ingredient
removing unit to supply the inert gas to the processing chamber
before sealing the processing chamber in order to remove an
ingredient facilitating the pyrolysis of the processing liquid from
the processing chamber after loading the substrate.
5. The supercritical processing apparatus as claimed in claim 3,
further comprising a controller to control the pyrolysis ingredient
removing unit to supply the inert gas to the processing chamber
after completion of loading the substrate into the processing
chamber and sealing the processing chamber, in order to remove an
ingredient facilitating the pyrolysis of the processing liquid from
the processing chamber.
6. The supercritical processing apparatus as claimed in claim 1,
wherein the processing chamber is received within a case in which
the substrate is loaded and unloaded through a loading/unloading
port, and the pyrolysis ingredient removing unit further comprises
a second gas supply unit to supply inert gas to the case in order
to remove the ingredient facilitating the pyrolysis of the
processing liquid from atmosphere surrounding the processing
chamber.
7. The supercritical processing apparatus as claimed in claim 1,
wherein the inert gas is nitrogen gas having a dew point of
-50.degree. C. or lower.
8. The supercritical processing apparatus as claimed in claim 1,
wherein the fluorine compound is hydrofluoro ether consisting of a
fluoroalkyl group including one or fewer carbon-carbon bond of a
carbon atom positioned at .alpha. location, and two or fewer
carbon-carbon bonds of a carbon atom positioned at .beta. location,
when viewed from an oxygen atom.
9. The supercritical processing apparatus as claimed in claim 8,
wherein the fluorine compound includes at least one hydrofluoro
ether selected from the group consisting of
1,1,2,2-tetrafluoro-1-(2,2,2-trifluoroethoxy)ethane,
1,1,2,3,3,3-hexafluoro-1-(2,2,2-trifluoroethoxy)propane, and
2,2,3,3,3-pentafluoro-1-(1,1,2,3,3,3-hexafluoropropoxy)propane.
10. A supercritical processing method, comprising: loading a
substrate formed with a pattern into a processing chamber; removing
an ingredient facilitating the pyrolysis of a processing liquid
from the processing chamber or from the processing liquid including
a fluorine compound supplied to the processing chamber; supplying
the processing liquid to the processing chamber where the substrate
is received; sealing the processing chamber and performing a
processing for the substrate with a supercritical fluid obtained by
heating a liquid supplied in the processing chamber; and
discharging the supercritical fluid by opening the processing
chamber, wherein the fluorine compound is hydrofluoro ether or
hydrofluoro carbon.
11. The supercritical processing method as claimed in claim 10,
wherein the removing step further comprises supplying inert gas to
the processing liquid and performing a bubbling process.
12. The supercritical processing method as claimed in claim 10,
wherein the removing step further comprises supplying inert gas to
the processing chamber.
13. The supercritical processing method as claimed in claim 12,
wherein the supplying step supplies the inert gas to the processing
chamber before the processing chamber is sealed after the substrate
is loaded into the processing chamber, in order to remove the
ingredient facilitating the pyrolysis of the processing liquid from
the processing chamber.
14. The supercritical processing method as claimed in claim 12,
wherein the supplying step supplies the inert gas to the processing
chamber after the processing chamber is sealed after the substrate
is loaded into the processing chamber, in order to remove the
ingredient facilitating the pyrolysis of the processing liquid from
the processing chamber.
15. The supercritical processing method as claimed in claim 12,
wherein the processing chamber is received within a case in which
the substrate is loaded and unloaded through a loading/unloading
port, and the supplying step further comprises supplying inert gas
to the case while the processing chamber is in an open state, in
order to remove the ingredient facilitating the pyrolysis of the
processing liquid from atmosphere surrounding the processing
chamber.
16. The supercritical processing method as claimed in claim 12,
wherein the inert gas is nitrogen gas having a dew point of
-50.degree. C. or lower.
17. The supercritical processing method as claimed in claim 10,
wherein the fluorine compound is hydrofluoro ether consisting of a
fluoroalkyl group including one or fewer carbon-carbon bond of a
carbon atom positioned at .alpha. location, and two or fewer
carbon-carbon bonds of a carbon atom positioned at .beta. location,
when viewed from an oxygen atom.
18. The supercritical processing method as claimed in claim 17,
wherein the fluorine compound includes at least one hydrofluoro
ether selected from the group consisting of
1,1,2,2-tetrafluoro-1-(2,2,2-trifluoroethoxy)ethane,
1,1,2,3,3,3-hexafluoro-1-(2,2,2-trifluoroethoxy)propane, and
2,2,3,3,3-pentafluoro-1-(1,1,2,3,3,3-hexafluoropropoxy)propane.
Description
[0001] This application is based on and claims priority from
Japanese Patent Application No. 2010-049567, filed on Mar. 5, 2010,
with the Japanese Patent Office, the disclosure of which is
incorporated herein in its entirety by reference.
TECHNICAL FIELD
[0002] The present disclosure relates to a technology for
processing a substrate, to such as a semiconductor wafer, formed
with a pattern on a surface with a supercritical fluid.
BACKGROUND
[0003] In manufacturing of large-scale and high performance
semiconductor devices including Large Scale Integrations (LSI) on a
surface of a substrate, e.g., a semiconductor wafer (hereinafter,
referred to as a "wafer"), it is necessary to form an ultra-fine
pattern on the surface of the wafer. The pattern is formed by
conducting a patterning process for the wafer coated with resist,
which includes various processes such as an exposure process, a
developing process, and a cleaning process. The wafer is then
etched to transfer the resist pattern to the wafer, thereby forming
the pattern on the surface of the wafer. After the etching process
of the wafer, a cleaning process is performed in order to remove
dusts or natural oxide films on the wafer.
[0004] In the cleaning process, for example, as schematically
illustrated in FIG. 12A, a wafer W formed with a pattern 11 on a
surface thereof is immersed in a processing liquid 101, such as a
chemical liquid or a rinse liquid, or processing liquid 101 is
supplied to the surface of wafer W. However, as the semiconductor
devices are highly integrated, there occurs a problem of a pattern
collapsing in which pattern 11 or the resist on the surface of the
wafer collapses during a drying process of the processing liquid,
after performing the cleaning process.
[0005] The pattern collapse refers to a phenomenon in which pattern
11 collapses toward the direction where larger quantity of
processing liquid is remained when the processing liquid on left
and right sides of pattern 11 is not uniformly dried after the
cleaning process is completed, because the balance of the capillary
force, which tensions pattern 11 in the left and right directions,
is lost. FIG. 12B illustrates a state in which the processing
liquid is dried on the outside regions of the left and right sides
in which pattern 11 is not formed, while the processing liquid
remains in the gap of pattern 11. As a result, pattern 11 on both
the left and right sides collapses inwardly by the capillary force
applied from the processing liquid left between patterns 11. The to
pattern collapse is also a problem in the field of the MEMS
(Micro-Electro-Mechanical System), which is manufactured by
application of semiconductor manufacturing technology.
[0006] The capillary force that causes the pattern collapse is
caused by the surface tension of the processing liquid applied in
liquid/air interface between, for example, the atmosphere
surrounding wafer W and the processing liquid left between patterns
11, after the cleaning process. Therefore, a processing method of
drying the processing liquid (hereinafter, referred to as "a
supercritical processing") by using fluid in a supercritical state
(supercritical fluid) in which interface is not formed between gas
and liquid has been attracting attention.
[0007] In the supercritical processing method, as illustrated in
FIG. 13A, for example, liquid on a surface of wafer W is
substituted with supercritical fluid 102 within a sealed chamber
and then supercritical fluid 102 is gradually discharged from the
chamber. As a result, the surface of wafer W is substituted in a
sequence of processing liquid.fwdarw.supercritical fluid.fwdarw.air
atmosphere, so that it is possible to remove the processing liquid
on the surface of wafer W without forming the liquid/air interface,
thereby preventing the generation of pattern collapse.
[0008] For the fluid used in the supercritical processing, carbon
oxide, hydrofluoro ether (HFE), hydrofluoro carbon (HFC), etc. are
used. However, carbon oxide in the supercritical state has low
miscibility with the processing liquid, so that there may be a case
in which the carbon oxide in the supercritical state makes it
difficult to substitute the processing liquid with the
supercritical fluid. In the meantime, a fluorine compound, such as
HFE or HFC, is satisfactorily miscible with the processing liquid,
but a part of the fluorine compounds is pyrolyzed at a high
temperature and a high pressure in which the processing liquid
becomes the supercritical state, so that there is a case in which,
for example, the fluorine compound discharges fluorine atoms in a
state of HF.
[0009] For example, as illustrated in FIG. 13A, in the event that
an SiO.sub.2 film 12 to is formed on the surface of wafer W, when
the fluorine atoms are emitted from the fluorine compound, there is
a concern that SiO.sub.2 film 12 is etched as illustrated in FIG.
13B. Further, the discharge of the fluorine atoms from the fluorine
compound results in the deterioration of the property of the
semiconductor device because the fluorine atoms may be injected
into the semiconductor device of wafer W or pattern 11. Especially,
when oxygen or moisture exists in the atmosphere in which the
supercritical processing is performed, the oxygen or moisture
becomes an ingredient facilitating the pyrolysis of the fluorine
compound, so that SiO.sub.2 film 12 may be easily etched or the
fluorine atoms may be easily injected into the device.
[0010] Japanese Laid-Open Patent Publication No. 2006-303316 (e.g.,
paragraphs 0035 through 0038) discloses a technology in which a
mixture liquid of HFE, such as HCF.sub.2CF.sub.2OCH.sub.2CF.sub.3,
CF.sub.3CHFCF.sub.2O CH.sub.2CF.sub.3, and
CF.sub.3CHFCF.sub.2OCH.sub.2CF.sub.2CF.sub.3, is made in the
supercritical state, the supercritical fluid is applied to a
substrate processed with the cleaning process, and the substrate is
dried. However, the disclosed technology does not take into account
the problem of the discharge of the fluorine atoms from HFE.
SUMMARY
[0011] According to one embodiment, there is provided a
supercritical processing apparatus, including: a sealable
processing chamber in which a processing is performed on a
substrate with a supercritical fluid; a liquid supply unit to
supply a processing liquid including a fluorine compound to the
processing chamber; a liquid discharge unit to discharge the
supercritical fluid from the processing chamber; a pyrolysis
ingredient removing unit to remove an ingredient facilitating the
pyrolysis of liquid supplied from the processing chamber or from
the liquid supply unit; and a heating unit to heat the liquid
supplied to the processing chamber, wherein the fluorine to
compound is hydrofluoro ether or hydrofluoro carbon.
[0012] The foregoing summary is illustrative only and is not
intended to be in any way limiting. In addition to the illustrative
aspects, embodiments, and features described above, further
aspects, embodiments, and features will become apparent by
reference to the drawings and the following detailed
description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a vertical-sectional view illustrating an example
of a wafer cleaning processing apparatus.
[0014] FIG. 2 is a vertical-sectional view illustrating a
supercritical processing apparatus according an embodiment.
[0015] FIG. 3 is a view illustrating a system of supply and
discharge of a processing liquid and inert gas for the
supercritical processing apparatus.
[0016] FIG. 4 is a flowchart illustrating an operation executed by
the supercritical processing apparatus.
[0017] FIG. 5 is a first view illustrating an operation of loading
a wafer into the supercritical processing apparatus.
[0018] FIG. 6 is a second view illustrating the operation of
loading a wafer into the supercritical processing apparatus.
[0019] FIG. 7 is a view illustrating contents of a supercritical
processing performed by the supercritical processing apparatus.
[0020] FIG. 8 is a view illustrating an example of a timing of
supply of inert gas to the supercritical processing apparatus.
[0021] FIG. 9 is a view illustrating another example of a timing of
supply of inert gas to the supercritical processing apparatus.
[0022] FIG. 10 is a structural formula of HFE according to an
embodiment.
[0023] FIG. 11 is a structural formula of HFE according to a
comparative to example.
[0024] FIG. 12 is a view illustrating a phase of generation of
pattern collapse.
[0025] FIG. 13 is a view illustrating a phase of a processing using
supercritical fluid.
DETAILED DESCRIPTION
[0026] In the following detailed description, reference is made to
the accompanying drawings, which form a part hereof. The
illustrative embodiments described in the detailed description,
drawings, and claims are not meant to be limiting. Other
embodiments may be utilized, and other changes may be made, without
departing from the spirit or scope of the subject matter presented
here.
[0027] The present disclosure has been made in consideration of the
above problems, and provides a supercritical processing apparatus
and a supercritical processing method which prohibit the generation
of pattern collapse or the insertion of material forming a
processing liquid into a substrate.
[0028] According to an embodiment of the present disclosure, the
supercritical processing apparatus of the present disclosure
includes: a sealable processing chamber in which a processing is
performed on a substrate with a supercritical fluid; a liquid
supply unit to supply a processing liquid including a fluorine
compound to the processing chamber; a liquid discharge unit to
discharge the supercritical fluid from the processing chamber; a
pyrolysis ingredient removing unit to remove an ingredient
facilitating the pyrolysis of the liquid from within the processing
chamber or within a liquid supplied from the liquid supply unit;
and a heating unit to heat the liquid supplied to the processing
chamber, wherein the fluorine compound is hydrofluoro ether or
hydrofluoro carbon.
[0029] The supercritical processing apparatus preferably includes
the following characteristics.
[0030] (a) The pyrolysis ingredient removing unit includes a
bubbling unit to supply inert gas to a processing liquid before the
processing liquid is supplied from the liquid supply unit and to
perform a bubbling process.
[0031] (b) The pyrolysis ingredient removing unit includes a first
gas supply unit to supply inert gas to the processing chamber.
[0032] (c) In case (b) above, the supercritical processing
apparatus includes a controller to control the pyrolysis ingredient
removing unit so that the inert gas is supplied to the processing
chamber before sealing of the processing chamber in order to remove
an ingredient, which facilitates the pyrolysis of the processing
liquid when the processing chamber is sealed after loading of the
substrate, from the processing chamber.
[0033] (d) In case (b) or (c), the supercritical processing
apparatus includes a controller to control the pyrolysis ingredient
removing unit so that the inert gas is supplied to the processing
chamber after completion of loading of the substrate into the
processing chamber and sealing of the processing chamber, in order
to remove an ingredient facilitating the pyrolysis of the
processing liquid from the processing chamber.
[0034] (e) The processing chamber is received within a case in
which the substrate is loaded and unloaded through a
loading/unloading port, and the pyrolysis ingredient removing unit
further includes a second gas supply unit to supply inert gas to
the case in order to remove an ingredient facilitating the
pyrolysis of the processing liquid from atmosphere surrounding the
processing chamber.
[0035] (f) In cases (b) to (e), the inert gas is nitrogen gas
having a dew point of -50.degree. C. or lower.
[0036] (g) The fluorine compound is hydrofluoro ether consisting of
a fluoroalkyl group including one or fewer carbon-carbon bond of a
carbon atom to positioned at .alpha. location and two or fewer
carbon-carbon bonds of a carbon atom positioned at .beta. location
when viewed from an oxygen atom.
[0037] (h) The fluorine compound includes at least one hydrofluoro
ether selected from the group consisting of
1,1,2,2-tetrafluoro-1-(2,2,2-trifluoroethoxy)ethane,
1,1,2,3,3,3-hexafluoro-1-(2,2,2-trifluoroethoxy)propane, and
2,2,3,3,3-pentafluoro-1-(1,1,2,3,3,3-hexafluoropropoxy)propane.
[0038] According to another embodiment of the present disclosure, a
supercritical processing method includes: loading a substrate
formed with a pattern into a processing chamber; removing an
ingredient facilitating the pyrolysis of a processing liquid from
the processing chamber or the processing liquid including a
fluorine compound supplied to the processing chamber; supplying the
processing liquid to the processing chamber where the substrate is
received; sealing the processing chamber and performing a
processing for the substrate with a supercritical fluid obtained by
heating a liquid supplied in the processing chamber; and
discharging the supercritical fluid by opening the processing
chamber, wherein the fluorine compound is hydrofluoro ether or
hydrofluoro carbon.
[0039] Further, removing of the ingredient facilitating the
pyrolysis of the processing liquid includes supplying inert gas to
the processing liquid and performing a bubbling process.
[0040] Further, the removing of the ingredient facilitating the
pyrolysis of the processing liquid includes supplying inert gas to
the processing chamber.
[0041] Further, supplying supplies the inert gas to the processing
chamber before the processing chamber is sealed after the substrate
is loaded into the processing chamber, in order to remove the
ingredient, which facilitates the pyrolysis of the processing
liquid.
[0042] The supplying supplies the inert gas to the processing
chamber after the to processing chamber is sealed after the
substrate is loaded into the processing chamber, in order to remove
the ingredient facilitating the pyrolysis of the processing liquid
from the processing chamber.
[0043] Further, the processing chamber is received within a case in
which the substrate is loaded and unloaded through a
loading/unloading port, and supplying the inert gas further
includes supplying inert gas to the case while the processing
chamber is in an open state of the processing chamber in order to
remove the ingredient facilitating the pyrolysis of the processing
liquid from atmosphere surrounding the processing chamber.
[0044] Preferably, the inert gas is nitrogen gas having a dew point
of -50.degree. C. or lower.
[0045] Preferably, the fluorine compound is hydrofluoro ether
consisting of a fluoroalkyl group including one or fewer
carbon-carbon bond of a carbon atom positioned at .alpha. location
and two or fewer carbon-carbon bonds of a carbon atom positioned at
.beta. location when viewed from an oxygen atom.
[0046] Preferably, the fluorine compound includes at least one
hydrofluoro ether selected from the group consisting of
1,1,2,2-tetrafluoro-1-(2,2,2-trifluoroethoxy)ethane,
1,1,2,3,3,3-hexafluoro-1-(2,2,2-trifluoroethoxy)propane, and
2,2,3,3,3-pentafluoro-1-(1,1,2,3,3,3-hexafluoropropoxy)propane.
[0047] Accordingly, the present disclosure uses the fluorine
compound, such as hydrofluoro ether (HFE) or hydrofluoro carbon
(HFC), and removes a factor facilitating the pyrolysis of the
fluorine compound from a processing system, so that it is possible
to perform the supercritical processing under a condition in which
the facilitation of a decomposition of the fluorine compound is
difficult. Therefore, when the pattern is formed on the surface of
the substrate, the present disclosure can control the generation of
the pattern collapse and the injection of the fluorine atoms into
the substrate, thereby to obtaining a high-quality processing
result.
[0048] Hereinafter, as an embodiment of the present disclosure, a
supercritical processing apparatus will be described, which removes
processing liquids attached to a wafer after a cleaning process
with a supercritical fluid of a fluorine compound, e.g. HFE. Prior
to specifically describing a construction of the supercritical
processing apparatus according to an embodiment of the present
disclosure, a single-type cleaning apparatus will be briefly
described, as an example of a cleaning process, which cleans wafers
one by one by spin cleaning.
[0049] FIG. 1 is a vertical-sectional view illustrating a
single-type cleaning apparatus 2. Single-type cleaning apparatus 2
holds a wafer W horizontally by a wafer holding mechanism 23
disposed within an outside chamber 21 forming a processing space
and rotates wafer holding mechanism 23 around a vertical shaft, to
rotate wafer W. Then, single-type cleaning apparatus 2 makes a
nozzle arm 24 to enter an upper side of rotating wafer W and
supplies a chemical liquid and a rinse liquid from a nozzle 241
installed at a front end of nozzle arm 24 in a preset sequence, to
perform a cleaning process on a surface of wafer W. Further, a
chemical liquid supply channel 231 is formed within wafer holding
mechanism 23, so that the back surface of wafer W is cleaned by a
chemical liquid and a rinse liquid supplied from chemical liquid
supply channel 231.
[0050] The cleaning process is performed in a sequence of, for
example, removal of particle or organic contaminants with SC1
liquid (a liquid mixture of ammonia and oxygenated water) of an
alkali chemical liquid.fwdarw.rinsing of wafer W with deionized
water (DIW) of a rinse liquid.fwdarw.removal of natural oxidized
film with diluted hydrofluoric acid (DHF) of an acid chemical
liquid.fwdarw.rinsing of wafer W with DIW. These liquids are
received within an inside cup 22 disposed within outside chamber 21
or outside chamber 21, and are discharged from liquid discharge
ports 221 and 211. Further, the atmosphere within outside chamber
21 is exhausted from a gas exhaust port 212.
[0051] A liquid, e.g., isopropyl alcohol (IPA), is supplied to the
surface of wafer W for which the cleaning process is completed, in
a state where the rotation of wafer holding mechanism 23 is
stopped, so that the IPA is substituted with DIW left on wafer W.
Further, for example, HFE, which is the same kind of HFE used in
the supercritical processing apparatus to be described later, is
supplied to the surface of wafer W, and the IPA is substituted with
the HFE, so that the surface of wafer W is coated with the HFE
liquid. Wafer W coated with the HFE liquid is then transferred to
an outside carrying apparatus by a transfer mechanism (not shown)
installed in wafer holding mechanism 23, so that wafer W is
unloaded from cleaning apparatus 2.
[0052] DIW on the surface of wafer W is substituted temporarily
with the IPA liquid, because the moisture facilitates the pyrolysis
of HFE if moisture remains when the HFE enters into the
supercritical state. Therefore, the moisture is removed from the
surface of wafer as much as possible by substituting DIW with the
IPA liquid, and then the IPA liquid is substituted with HFE, such
that the amount of moisture introduced into the supercritical
processing apparatus decreases as much as possible. Here, while
alcohol, such as IPA, still has an effect facilitating the
pyrolysis of HFE in the supercritical state, such a facilitating
action is insignificant in comparison with the effect of the
moisture. Further, for example, when a sufficient quantity of HFE
can be used for removing DIW, the substitution of DIW with IPA may
be omitted and DIW of the surface of wafer W may be substituted
with HFE directly.
[0053] After completing the cleaning process in cleaning apparatus
2, Wafer W is carried to the supercritical processing apparatus
while the surface thereof is coated with HFE, and a supercritical
processing is performed to remove the processing liquid attached to
the surface of the wafer. Hereinafter, a construction of a
supercritical processing apparatus 3 will be described with
reference to FIGS. 2 and 3, according to an embodiment.
[0054] Supercritical processing apparatus 3 includes an upper
chamber 31 and a bottom plate 32 of upper chamber 31 in which the
supercritical processing is performed for wafer W. Supercritical
processing apparatus 3 further includes a mechanism for storing
wafer W within upper chamber 31, and a mechanism for supplying HFE
of a processing liquid to upper chamber 31 and inducing HFE to
enter into the supercritical state.
[0055] Upper chamber 31 and bottom plate 32 correspond to a
processing chamber according to the present embodiment, and the
supercritical processing is performed in the processing chamber by
storing wafer W and removing liquid (HFE coated in cleaning
apparatus 2 in the present embodiment) attached to the surface of
wafer W by using HFE in the supercritical state. Upper chamber 31
is a pressure-resistant chamber shaped like a flat disk, in which a
concave portion is formed at the lower surface thereof forming a
processing space 30 for the supercritical processing for wafer W,
and is made of, for example, stainless steel. The concave portion
formed on the lower surface of upper chamber 31 is shaped like, for
example, a flat disk, and is combined with a disposition board 321
of wafer W to be described later, so that processing space 30 for
storing wafer W having a diameter of 300 mm is formed between upper
chamber 31 and bottom plate 32. Upper chamber 31 may be metal
coated by gold, platinum, Teflon (registered trademark)-coated,
resin-coated by polyimide or ETHOXY resin, so that the emission of
fluorine atoms from HFE can be suppressed.
[0056] As illustrated in FIG. 2, upper chamber 31 includes three
flow channels 311, 312, and 313 opened toward the side face of
processing space 30. Reference number 311 denotes an HFE supply
channel for supplying HFE of a processing liquid to processing
space 30 in a liquid state, reference number 312 denotes an HFE
discharge channel for discharging supercritical HFE from processing
space 30, and reference number 313 denotes a discharge channel for
discharging atmosphere within processing space 30 from processing
space 30 before and after the processing.
[0057] As illustrated in FIG. 3, HFE supply channel 311 is
connected to an HFE supply unit 4 through an HFE supply line 42
provided with a blocking valve 421. Each device from HFE supply
unit 4 to HFE supply channel 311 corresponds to a liquid supply
unit for supplying HFE to processing space 30 (within the
processing chamber) according to the present embodiment. Further,
HFE discharge channel 312 is connected to HFE supply unit 4 through
an HFE collection line 43 provided with a blocking valve 431 and a
cooling unit 432, and can recycle HFE. Cooling unit 432 cools down
HFE discharged from processing space 30, for example, in the
supercritical state or a gaseous state, and collects HFE in a
liquid state. Each device from HFE discharge channel 312 to HFE
supply unit 4 corresponds to a fluid discharge unit of the present
embodiment.
[0058] HFE supply unit 4 is provided with a pressurized gas supply
line 401 for carrying pressurized HFE toward the processing
chamber. Pressurized gas supply line 401 supplies the pressurized
carrier gas, such as nitrogen gas, to a reservoir forming HFE
supply unit 4 in a state where an exhaust line 412 is closed by,
for example, an opening/closing valve (not shown), so that the
inside HFE can be delivered to the processing chamber. Descriptions
for exhaust line 412 will be followed. The supply amount of HFE can
be controlled, for example, by increasing or decreasing the
quantity of nitrogen gas supplied from carrier gas supply line 401.
Here, a method of supplying HFE to the processing chamber is not
limited to the use of the pressurized gas, and it is acceptable to
install a liquid feeding pump in HFE supply line 42 and supply HFE
through the liquid feeding pump.
[0059] Further, an outlet side of discharge channel 313 is
connected to a discharge line 44 via a blocking valve 441 and a gas
collection unit 442, and discharge line 44 is connected to, for
example, a detoxifying facility of a factory. Gas collection unit
442 is formed with, for example, an absorption column filled with
activated carbon, thereby absorbing HFE included in the gas
discharged from processing space 30. HFE adsorbed to the activated
carbon can be collected by, for example, passing steam that passes
through gas collection unit 442 in a state where gas collection
unit 442 is off-line to with respect to discharge line 44, and
desorbing HFE from the activated carbon, so as to cool the
steam.
[0060] As described above, in the present embodiment, it is
exemplified that HFE supply channel 311, HFE discharge channel 312,
and discharge channel 313 are installed in a side of HFE supply
channel 311, but these channels 311, 312, and 313 can be installed
at the side of bottom plate 32 as a matter of choice.
[0061] As illustrated in FIG. 2, upper chamber 31 is fixed to an
upper surface of case 38, which includes a pressing member 381
shaped like a cantilever that is crossed in a cross shape and
receives the entire upper chamber 31. Pressing member 381 resists
against the force applied from the supercritical fluid within
processing space 30 and presses upper chamber 31 downwardly.
[0062] Bottom plate 32 closes the concave portion of upper chamber
31 in a lower side, forming processing space 30 for receiving and
holding wafer W. Bottom plate 32 is made of, for example, stainless
steel, and is formed with, for example, a round plate-shaped member
larger than the opened surface of the concave portion of upper
chamber 31. Disposition board 321, which is shaped like a round
plate capable of being assembled within the concave portion of
upper chamber 31 and is made of, for example, stainless steel, is
fixed to an upper surface of bottom plate 32. As illustrated in
FIG. 2, a concave portion constituting a disposition area 323 of
wafer W is formed at the upper surface of disposition board
321.
[0063] Further, bottom plate 32 can be moved up and down by a
bottom plate elevating mechanism 35 including a support pole 351
and a driving mechanism 352 of support pole 351, and can move
between a lower transfer position at which a carrying apparatus
(not shown) transfers wafer W subjected to the cleaning process by
cleaning apparatus 2 to bottom plate 32, and a processing position
at which wafer W is subjected to a supercritical processing in
processing space 30 formed by closing the concave portion of upper
chamber 31.
[0064] Reference number 34 of FIG. 2 denotes a guide member guiding
an to elevating orbit of bottom plate 32 in an elevation operation,
and for example, guide members 34 are arranged at, for example,
three locations with substantially identical interval along the
circumference of bottom plate 32.
[0065] Here, the pressure within processing space 30 where the
supercritical processing is being performed, is in such a high
pressure, for example, an absolute pressure equivalent to 3 MPa,
and a large downward force is applied to bottom plate 32.
Therefore, a support mechanism 33 for supporting a bottom surface
of bottom plate 32 is installed at the lower side of bottom plate
32. Supporting mechanism 33 includes a supporting member 331 for
supporting the bottom surface of bottom plate 32, sealing
processing space 30 and elevating in accordance with an elevating
movement of bottom plate 32, a guide member 332 for guiding an
alleviation orbit of supporting member 331, and a driving mechanism
333 including, for example, a hydraulic pump. Supporting mechanism
33, similar to aforementioned guide member 34, is arranged at, for
example, three locations in a substantially identical interval
along the circumference of bottom plate 32.
[0066] A lifter 361 is installed at the center of bottom plate 32
for transferring wafer W to the outside carrying device. Lifter 361
passes through the substantially center area of bottom plate 32 and
disposition board 321 in a vertical direction, a round plate-shaped
wafer holding unit 363 is fixed to the upper end of lifter 361 for
horizontally holding wafer W, and a driving mechanism 362 of lifter
361 is installed at the lower end of lifter 361.
[0067] Disposition board 321 includes a concave portion for storing
wafer holding unit 363 formed at the center of an upper surface
thereof, and by independently elevating lifter 361 from bottom
plate 32, wafer holding unit 363 protrudes and depresses from
bottom plate 32 so that it is possible to transfer wafer W between
the outside carrying device and disposition area 323 on bottom
plate 32. Here, as illustrated in FIG. 2, when wafer holding unit
363 is stored within the concave part of bottom plate 32, an upper
surface of wafer holding unit 363 is identical to that of
disposition board to 321 serving as disposition area 323.
[0068] Further, a heater 322 is laid in an inside of bottom plate
32. Heater 322 includes, for example, a resistive heating element
for increasing the temperature of HFE supplied to processing space
30 to, for example, 200.degree. C., increasing the pressure of
processing space 30 to, for example, 3 MPa by the expansion of the
HFE fluid, and inducing the processing liquid to enter into the
supercritical state. As illustrated in FIG. 3, heater 322 is
connected to a power unit 6 and generates heat by power supplied
from power unit 6, so that it is possible to heat HFT within
processing space 30 through disposition board 321 and wafer W
arranged on the upper surface of disposition board 321. Heater 322
corresponds to a heating unit of the present embodiment.
[0069] In order to suppress the discharge of the fluorine atoms by
the pyrolysis of HFE as described in the background art,
supercritical processing apparatus 3 including the aforementioned
construction according to the present embodiment adopts a special
construction for eliminating the ingredient facilitating the
pyrolysis of HFE from both sides of HFE used as fluid for the
supercritical processing and the apparatus.
[0070] Prior to specifically describing the construction of an
apparatus installed for eliminating the ingredient facilitating the
pyrolysis of HFE, the relation between fluorine compounds, such as
HFE or HFC, and an ingredient facilitating the pyrolysis of the
fluorine compound will be described.
[0071] A liquid of a fluorinated compound having no risk of
flammability and low toxicity includes hydrofluoro ether
(constituting with carbon, hydrogen, fluorine, and ether oxygen,
and having a COC bond) and hydrofluoro carbon (constituting with
carbon, hydrogen, and fluorine). Hydrofluoro ether includes, for
example, CF.sub.3CF.sub.2CH.sub.2OCHF.sub.2,
CF.sub.3CF.sub.2OCH.sub.2CF.sub.3, C.sub.3F.sub.7OCH.sub.3,
C.sub.4F.sub.9OCH.sub.2CH.sub.3,
(CF.sub.3).sub.2CFCF(OCH.sub.3)CF.sub.2CF.sub.3,
CHF.sub.2CF.sub.2OCH.sub.2CF.sub.3, CF.sub.3CHFOCHF.sub.2, etc. and
hydrofluoro carbon includes, for example, C.sub.4F.sub.9H,
C.sub.5F.sub.11H, C.sub.6F.sub.13H, C.sub.4F.sub.9CH.sub.2CH.sub.3,
C.sub.6F.sub.13CH.sub.2CH.sub.3, CF.sub.3CH.sub.2CF.sub.2CH.sub.3,
c-C.sub.5F.sub.7H.sub.3, CF.sub.3CF.sub.2CHFCHFCF.sub.3,
CF.sub.3CH.sub.2CHF.sub.2, etc., and they are liquid at a normal
temperature and pressure. Further, the fluorine compounds are to
materials having a short atmospheric lifetime of several years
(perfluorocarbon generally has an atmospheric lifetime of 1000 to
50,000 years) and having no environmental problem. When the
hydrofluoro ether or hydrofluoro carbon is present under a
predetermined temperature and pressure, the fluorine compounds
enter into the supercritical state, and then by decreasing the
pressure to air pressure, it is possible to perform the
supercritical processing of drying wafer W after the liquid
processing is performed.
[0072] Examples of commercially available hydrofluoro ether
(fluoroalkyl chain is C.sub.6 or fewer), which is easy to use
because having a boiling point of 50.degree. C. or higher and a
critical temperature of about 200.degree. C. or lower, include
those shown in Table 1.
TABLE-US-00001 TABLE 1 Boiling point and critical point (critical
temperature, critical pressure) of representative hydrofluoro ether
Boiling Critical Critical point temperature pressure Molecular
structure (.degree. C.) (.degree. C.) (atm) C.sub.4F.sub.9OCH.sub.3
61 185 19.5 C.sub.4F.sub.9OCH.sub.2CH.sub.3 76 198 18.2
(CF.sub.3).sub.2CFCF(OCH.sub.3)CF.sub.2CF.sub.3 98 211 13.9
CF.sub.3CH.sub.2OCF.sub.2CHF.sub.2 56 188 23.4
CF.sub.3CH.sub.2OCF.sub.2CHFCF.sub.3 73 197 22.2
CF.sub.3CHFCF.sub.2OCH.sub.2CF.sub.2CF.sub.3 88 203 18.5
[0073] In order to make any hydrofluoro ether to become the
supercritical state, it is necessary to increase the temperature to
at least 185.degree. C., and close to 200.degree. C. .
[0074] Further, hydrofluoro carbon, which especially has a boiling
point of 50.degree. C. or higher and has been put on the market, is
represented in Table 2.
TABLE-US-00002 TABLE 2 Boiling point and critical point (critical
temperature, critical pressure) of representative hydrofluoro
carbon Boiling critical critical point temperature pressure
Molecular structure (.degree. C.) (.degree. C.) (atm)
C.sub.6F.sub.13H 71 188 15.7 C.sub.4F.sub.9CH.sub.2CH.sub.3 68 195
18.6 C.sub.6F.sub.13CH.sub.2CH.sub.3 114 233 14.1
c-C.sub.5F.sub.7H.sub.3 83 -- -- CF.sub.3CF.sub.2CHFCHFCF.sub.3 55
181 22.6
[0075] While there is a hydrofluoro carbon of which the critical
temperature has not been identified among the hydrofluoro carbons
represented in Table 2, the critical temperature of most
hydrofluoro carbons is around 200.degree. C., similar to the
hydrofluoro to ethers represented in Table 1.
[0076] It has been known that the liquid of the fluorine compound
represented by hydrofluoro ether or hydrofluoro carbon generally
has a high thermo-stability, but it can be noted that acid
contents, even though they are very small amount, are generated by
an oxidation process under the existence of oxygen in a temperature
range (around 200.degree. C.) where the supercritical state is
achieved used in the present embodiment. In the meantime, when an
identical process is actually performed while oxygen is not
presented, the generation of the acid contents is not observed at
all, indicating that the oxidation decomposition does not
occur.
[0077] Therefore, as a preliminary experiment, a thermo-stability
test was performed with respect to hydrofluoro ethers or
hydrofluoro carbons represented in Table 3. The thermo-stability
test was performed by filling a pressure resistant chamber made of
SUS-304 with a sample of the liquid of hydrofluoro ether and the
liquid of hydrofluoro carbon at 200.degree. C. for 72 hours under
the conditions represented in Table 3. The chamber was filled with
the sample, a quantity of which is smaller than the total volume of
the chamber, so as to form a vapor atmosphere within the
pressure-resistant chamber. Then, the test was performed under two
conditions including a vapor atmosphere containing about 20 vol %
oxygen and a vapor atmosphere containing an oxygen with a
concentration of 50 vol ppm or less (all remaining portions are
nitrogen gas). Further, for various kinds of fluorine compounds
used as the sample of the thermo-stability test, the quantity of
dissolved oxygen was reduced up to the degree as shown in Table 3
by bubbling argon gas within the sample liquid.
[0078] A result of evaluation of acid contents and increment of F
ions is represented in Table 3. The acid contents and the increment
of F ions are obtained by measuring pH of extracted water and the
concentration of fluorine ion, through an operation of extracting
the sample after the test with an identical quantity of water.
TABLE-US-00003 TABLE 3 Result of thermo-stability test Concen-
Concentration tration Concen- of F ion after of moisture tration
test within of oxygen pH (lowest limit sample within after of
detection Fluorine compound (prior to test) atmosphere test is 0.5
ppm) CH.sub.3CH.sub.2OCF.sub.2CHF.sub.2 Saturation 20% 3~4 0.5 ppm
or less CF.sub.3CH.sub.2OCF.sub.2CHF.sub.2 Saturation <50 ppm 7
0.5 ppm or less CF.sub.3CH.sub.2OCF.sub.2CHF.sub.2 <50 ppm 20%
3~4 0.5 ppm or less CF.sub.3CH.sub.2OCF.sub.2CHF.sub.2 <50 ppm
<50 ppm 7 0.5 ppm or less C.sub.4F.sub.9OCH.sub.3 Saturation 20%
2~3 2~10 ppm C.sub.4F.sub.9OCH.sub.3 Saturation <50 ppm 5~6 0.5
ppm or less C.sub.4F.sub.9OCH.sub.3 <50 ppm 20% 2~3 ~1 ppm
C.sub.4F.sub.9OCH.sub.3 <50 ppm <50 ppm 6~7 0.5 ppm or less
C.sub.6H.sub.13H <50 ppm 20% 4~5 0.5 ppm or less
C.sub.6F.sub.13H <50 ppm <50 ppm 7 0.5 ppm or less
[0079] According to the result of Table 3, (1) regardless of the
moisture concentration value, when the oxygen concentration is low
within the atmosphere, the pH value is about 7 so that the
generation of the acid contents is suppressed, (2) when the oxygen
concentration in CF.sub.3CH.sub.2OCF.sub.2CHF.sub.2 and
C.sub.6F.sub.13H is 50 ppm or less, the pH value is about 7 and the
generation of the acid contents is not observed, and (3) when the
oxygen concentration C.sub.4F.sub.9OCH.sub.3 is 50 ppm or less,
while the generation of the acid contents is suppressed, the pH
value is from 6 to 7, so that it can be noted that the generation
of the acid contents is not completely suppressed.
[0080] According to the result of the thermo-stability test, the
oxygen concentration may be decreased within the vapor atmosphere
in order to suppress the generation of HF (the acid contents). It
is considered that when the oxygen concentration is high within the
vapor atmosphere, the oxygen is dissolved into the liquid of the
fluorinated compound, so that the oxidation of the fluorinated
liquid is facilitated. Therefore, it is important to decrease the
dissolved oxygen of the liquid itself of the fluorinated compound
and decrease the oxygen within the processing atmosphere in the
processing chamber.
[0081] Further, because each of the aforementioned fluorine
compounds is expensive, the fluorine compounds are collected by,
for example, aforementioned gas collection unit 442 in an activated
carbon absorption type as shown in FIG. 3, so that the discharge of
the fluorine compounds to the environment is suppressed. The
fluorine compounds collected by the activated carbon are collected
by a steam desorption. Therefore, in order to investigate the
thermo-stability of the fluorine compound in the stream desorption
processing, the thermo-stability was evaluated in the heat
treatment at 120.degree. C. for 72 hours under the existence of the
activated carbon by analyzing the acid contents and the F ion mass
after the test.
[0082] As a result, as illustrated in an embodiment to be described
later, it was identified that the acid contents of 160 ppm, the F
ion mass of 45 ppm, and HF by the dissolution were generated in
C.sub.4F.sub.9OCH.sub.3. In the meantime, it was identified that
CF.sub.3CH.sub.2OCF.sub.2CHF.sub.2 (FIG. 10A),
CF.sub.3CH.sub.2OCF.sub.2CHFCF.sub.3 (FIG. 10B), and
CF.sub.3CHFCF.sub.2OCH.sub.2CF.sub.2CF.sub.3 (FIG. 10C) were
difficult to be dissolved, and for example, it was identified that
both of the acid contents and the F ion mass were equal to or less
than a detection limit (1 ppm of acid contents, 0.02 ppm of F ion
mass) in the stability test under the same condition (120.degree.
C.) described above.
[0083] C.sub.4F.sub.9OCH.sub.3 used in the aforementioned
thermo-stability test is the mixture of
(CF.sub.3).sub.2CFCF.sub.2OCH.sub.3 (FIG. 11A) having a branched
structure and CF.sub.3CF.sub.2CF.sub.2CF.sub.2OCH.sub.3 having a
straight-chain structure. However, it is presumed that the reason
why the generation of HF in C.sub.4F.sub.9OCH.sub.3 has been
identified is that C.sub.4F.sub.9OCH.sub.3 includes
(CF.sub.3).sub.2CFCF.sub.2OCH.sub.3 in which the carbon within the
fluoroalkyl chain positioned at .alpha. position or .beta. position
of ether oxygen has a branched structure, and thus the fluorine
atom combined with the branched carbon is easily separated as HF.
Hydrofluoro ether from which HF is easily separated is not limited
to what is represented in FIG. 11A, and it can be noted that, for
example, the hydrofluoro ether shown in FIG. 11B or FIG. 11C, in
which the carbon within the fluoroalkyl chain positioned at .alpha.
position or .beta. position of ether oxygen has the branch
structure, is also dissolved so that HF is easily emitted.
[0084] In comparison of the chemical structures between hydrofluoro
ether illustrated in FIGS. 10A to 10C suitable for the critical
processing and easily pyrolyzed hydrofluoro ether illustrated in
FIGS. 11A to 11C, it can be noted that in the easily pyrolyzed
hydrofluoro ether, a hydrofluoro group is branched to the carbon
atom positioned at .alpha. position or .beta. position as viewed
from the oxygen atom on at least one side of each fluoroalkyl group
combined with the oxygen atom.
[0085] In contrast, the hydrofluoro ether illustrated in FIGS. 10A
to 10C, which is stable in the supercritical state, does not have
the branch and the hydrofluoro group has the straight-chain shape
in both of the carbon atoms at .alpha. position and .beta.
position, as viewed from the oxygen atom. In expressing the
hydrofluoro ether with the number of carbon-carbon bonds of the
carbon atom at each position, the thermo-stable hydrofluoro ether
is formed with the fluoroalkyl group including one or fewer
(including zero) carbon-carbon bond of the carbon atom positioned
at .alpha. position and two or fewer (including zero) of
carbon-carbon bonds of the carbon atom positioned at .beta.
position, as viewed from the oxygen atom. Further, the hydrofluoro
ether having the above structure is difficult to be dissolved in
the supercritical state or in the steam desorption from the
activated carbon, so that it can be considered that hydrofluoro
ether is suitable for the supercritical processing according to the
present embodiment.
[0086] Among CF.sub.3CH.sub.2OCF.sub.2CHF.sub.2,
CF.sub.3CH.sub.2OCF.sub.2CHFCF.sub.3, and
CF.sub.3CHFCF.sub.2OCH.sub.2CF.sub.2CF.sub.3 which are difficult to
be pyrolyzed,
CF.sub.3CH.sub.2OCF.sub.2CHF.sub.2(1,1,2,2-tetrafluoro-1-(2,2,2-trifluoro-
ethoxy)ethane) has the lowest critical point, so that the
hydrofluoro ether can be easily used. Hereinafter, it is assumed
that CF.sub.3CH.sub.2OCF.sub.2CHF.sub.2 is supplied from HFE supply
unit 4 in supercritical processing apparatus 3 according to the
present embodiment will be described.
[0087] According to the result of the above investigation, the
dissolved oxygen is removed from the liquid or the oxygen is
removed from the processing atmosphere in which the supercritical
processing is performed by using the liquid of the fluorine
compounds which are difficult to be pyrolyzed (HFE in supercritical
processing apparatus 3 according to the embodiment), so that the
pyrolysis of HFE is suppressed, thereby suppressing the generation
of a problem of etching of wafer W by HF separated from HFE or
injection of the fluorine atoms into a semiconductor device.
[0088] Prior to describing the specific construction installed in
supercritical processing apparatus 3 according to the present
embodiment for suppressing the pyrolysis of HFE, a method of
decreasing the dissolved oxygen within HFE and removing the oxygen
from the inside of the processing chamber will be investigated.
First, as a method of decreasing the dissolved oxygen within the
processing liquid, for example, the liquid of the fluorine compound
is filled into a sealable chamber, and inert gas is introduced and
bubbled within the liquid, so that the oxygen dissolved within the
liquid is discharged. The time for the bubbling is, for example,
from five to ten minutes, and by sealing and pressurizing the
chamber so as to prevent the introduction of the outside oxygen
(air), it is possible to decrease the concentration of the
dissolved to oxygen. While nitrogen, helium, argon, etc. can be
used as the inert gas used for the bubbling, argon has a large
specific gravity in comparison with oxygen so that argon may be
used for a better oxygen substitution efficiency, and nitrogen gas
may be used for a lower cost.
[0089] Further, in order to suppress the dissolved oxygen, the
sealable chamber is filled with the liquid of the fluorine
compound, cooled down to near the melting point, and then vacuum
depressurized. The dissolved gas, such as oxygen, is then removed
from the system, and the chamber is sealed so as to prevent the
introduction of the outside oxygen (air). Further, for example, in
the event of the adoption of the construction of an apparatus
collecting HFE in an exclusive collection chamber, etc., it is also
efficient to decrease the dissolved oxygen within a collected
liquid through introducing the inert gas, such as argon, into the
collection chamber.
[0090] Next, in a method of removing oxygen from a processing
atmosphere in which the supercritical processing is performed, a
sealed chamber (corresponding to, for example, HFE supply unit 4 of
FIG. 3) storing HFE is connected to the processing chamber
(corresponding to upper chamber 31 and bottom plate 32 in the
present example) of supercritical processing apparatus 3, and inert
gas such as nitrogen or argon is introduced into the processing
chamber, so as to decrease the concentration of oxygen. Then, wafer
W is loaded into the processing chamber, the chamber is sealed, and
then HFE is introduced from the sealed chamber to the processing
chamber through a pipe. For example, the inert gas maintains its
introduced state until the processing chamber is sealed, preventing
oxygen from introducing into the processing chamber. After the
sealing of the processing chamber, the introduction of nitrogen is
stopped and the temperature of the processing chamber is increased
up to the critical point, to perform the processing.
[0091] Here, the pyrolysis of the fluorine compounds (HFE or HFC)
becomes noticeable in the existence of oxygen as described above.
Furthermore, the pyrolysis of the fluorine compounds also occurs in
the existence of water or alcohol. Especially, when the liquid of
the fluorine compound having an easily oxidizable structure is used
as a processing liquid for the supercritical processing, the
decrease of water or alcohol is important even if it is not as
important as the effect of the dissolved oxygen. This is because
water or alcohol is the supply sources for a proton (hydrogen ion)
so that HF is easily generated.
[0092] Especially, the existence of water easily creates the
pyrolysis of the fluorine compounds, so that the moisture may be
removed from the atmosphere in which the supercritical processing
is performed to prevent the introduction of the moisture. Water
molecules may be removed because water molecules absorbed to a
wafer W to be processed or to an inner wall of the processing
chamber along with a high humidity environment serves as a factor
creating the pyrolysis of the fluorine compounds. For example, as
discussed above, the moisture may be removed by substituting DIW
left on the surface of wafer W with IPA or HFE after the liquid
processing of wafer W, or by substituting the atmosphere inside of
the processing chamber with fully dried air or nitrogen before
wafer W is loaded into the processing chamber. Further, the
moisture is removed by substituting and purging the atmosphere of
the inside of the processing chamber with dry air or nitrogen
having a sufficiently low dew point even after the loading of wafer
W in the processing chamber. Furthermore, the introduction of
outside moisture may be suppressed by making the atmosphere within
supercritical processing apparatus 3 including the processing to
chamber such as, for example, the atmosphere within a case 38
illustrated in FIG. 2, to have a low humidity.
[0093] In the meantime, when the processing chamber is opened to
the air in loading/unloading wafer W, moisture may be absorbed to
the inner wall of the processing chamber, which becomes a problem
when a following wafer W is processed. Therefore, the temperature
of wafer W to be processed or the temperature of the inside of the
processing chamber may be increased before the liquid of the
fluorine compound is introduced for the supercritical processing,
thereby suppressing the moisture absorption. Specifically, it is
possible to conceive the control of the temperature of the inner
wall (top plate, side wall, bottom part, etc.) of the processing
chamber or the plate holding unit (disposition board 321 of FIG.
2), so as to suppress the moisture absorption.
[0094] Taking the above investigated result into consideration,
supercritical processing apparatus 3 according to the present
embodiment includes various constructions for (A) reducing the
dissolved oxygen within HFE, (B) removing oxygen or moisture from
processing space 30 within the processing chamber (upper chamber 31
and bottom plate 32) in which the supercritical processing is
performed, and (C) suppressing the moisture absorption to the wall
of the processing chamber, so that the pyrolysis of HFE may be
suppressed. These constructions correspond to a pyrolysis
ingredient removing unit according to the present embodiment.
Hereinafter, a specific construction of the pyrolysis ingredient
removing unit will be described.
[0095] A bubbling unit 41, serving as the pyrolysis ingredient
removing unit for reducing the dissolved oxygen within HFE
according to construction (A) as described above, for removing the
dissolved oxygen from HFE stored in HFE supply unit 4 is to
installed in HFE supply unit 4. Bubbling unit 41 is formed with,
for example, an exhaust pipe including multiple small holes formed
at the wall of a round pipe, and is connected to an inert gas
supply line 411 for supplying the inert gas (nitrogen gas in the
present example).
[0096] The nitrogen gas supplied from inert gas supply line 411 is
scattered and supplied into HFE in the inside of HFE supply unit 4
through bubbling unit 41. In this respect, the dissolved oxygen
within the vapor of the nitrogen gas in HFE is diffused, so that
the dissolved oxygen is removed. Reference number 412 of FIG. 3
denotes an exhaust line 412 for exhausting the nitrogen gas after
the bubbling from HFE supply unit 4.
[0097] Further, supercritical processing apparatus 3 includes a
mechanism, serving as the pyrolysis ingredient removing unit for
removing oxygen or moisture from processing space 30 disposed
within the processing chamber (upper chamber 31 and bottom plate
32) according to construction (B) as described above, for supplying
inert gas to processing space 30 during a period in which HFE is
not supplied to processing space 30. For example, HFE supply
channel 311 supplying HFE to processing space 30 is switchably
connected to an inert gas line 45 for supplying the inert gas to
processing space 30 and to aforementioned HFE supply line 42,
through a switching valve 422 installed in an upstream side of
blocking valve 421.
[0098] A high-purity nitrogen gas, which has a dew point controlled
to be equal to or lower than -50.degree. C., for example,
-60.degree. C., and contains oxygen at a level equivalent to about
several sub ppm, can be supplied to inert gas line 45 and can be
then supplied to processing space 30. The reason of supplying the
inert gas to processing space 30 in a heated state is to maintain
the heated state of upper chamber 31 or disposition board 321 to
that has been heated by heaters 314 and 322, as described later.
Further, since the supplied nitrogen gas serving as the inert gas
should include moisture as little as possible, it is not necessary
to specially set the lowest limit of the dew point, and the inert
gas supplied to processing space 30 is discharged to discharge line
44 through, for example, discharge channel 313.
[0099] Next, supercritical processing apparatus 3 has a function,
serving as the pyrolysis ingredient removing unit for suppressing
the moisture absorption to the wall surface of the processing
chamber according to the construction (C) as described above, for
heating a member constituting upper chamber 31 and disposition
board 321 even during a period in which the supercritical
processing is not performed. In supercritical processing apparatus
3 according to the present example, for example, with respect to
upper chamber 31, it is possible to heat disposition board 321 by
using aforementioned heater 322 installed within bottom plate
32.
[0100] In the meantime, heater 314 including, for example, the
resistant heating element is embedded in upper chamber 31 and as
illustrated in FIG. 3, and upper chamber 31 may be heated by heater
314 that emits heat by power supplied from power unit 6. Further,
as described above, a heater 452, in which, for example, a
resistant heating element is wound, is installed in inert gas line
45 that supplies the inert gas, so that it is possible to heat the
surface of upper chamber 31 or disposition board 321 by heating the
inert gas (nitrogen gas) to, for example, 100.degree. C. and
introducing heat energy into processing space 30.
[0101] While each of aforementioned heaters 322, 314, and 452
corresponds to a heating unit of the processing chamber (upper
chamber 31 and bottom plate 32), it is not necessary to install all
of three heaters 322, 314, and 452 for heating upper chamber to 31
and disposition board 321 forming processing space 30. For example,
it is possible to heat upper chamber 31 and disposition board 321
by using any one or two heaters among heaters 322, 314, and
452.
[0102] Further, as illustrated in FIG. 2, inert gas supply chamber
39 for passing the inert gas through case 38 is installed in a
ceiling part of case 38 storing upper chamber 31 and bottom plate
32. Inert gas supply chamber 39 includes one pyrolysis ingredient
removing unit, such as the pyrolysis ingredient unit according to
the construction (B) as described above, for removing oxygen or
moisture from processing space 30. For example, the nitrogen gas of
which the dew point is controlled to be equal to or lower than
-50.degree. C., for example, -60.degree. C., is supplied to inert
gas supply chamber 39.
[0103] The inert gas supplied to inert gas supply chamber 39 is
supplied to case 38 through plural air supply holes 391 formed at
the ceiling surface of case 38, so that for example, the inert gas
is exhausted from an exhaust unit 383 installed at the side wall of
the lower side of case 38. Through the construction, a down flow of
the inert gas is formed within case 38 flowing from the upper side
to the lower side of case 38, so that, for example, when bottom
plate 32 descends to a transfer position to open processing space
30 while wafer W is loaded and unloaded, it is possible to suppress
the introduction of oxygen or moisture into processing space
30.
[0104] Supercritical processing apparatus 3 including the
aforementioned construction is connected to a controller 7 as
illustrated in FIGS. 2 and 3. Controller 7 includes a computer
equipped with a CPU (not shown) and a memory unit (not shown), and
the memory unit records a program including programmed step
(command) groups related to the control of the operations of
supercritical processing apparatus 3 such as to the operations from
loading wafer W into supercritical processing apparatus 3,
performing the supercritical processing by using HFE, and to
unloading wafer W.
[0105] Further, controller 7 records a program for enabling
controller 7 to control a first gas supply unit (switching valve
422, etc.) for removing oxygen or moisture from processing space 30
and supplying the inert gas to processing space 30 for a
predetermined period time, and for enabling controller 7 to control
the heating unit (heaters 322, 314, and 452) of the processing
chamber (upper chamber 31 and bottom plate 32) to heat upper
chamber 31 and disposition board 321 for a predetermined period of
time. Each of the programs is stored in a memory medium, such as
hard disk, compact disk, magneto-optical disk, or memory card, and
is installed in a computer from the memory medium.
[0106] Hereinafter, the operation of supercritical processing
apparatus 3 will be described with reference to the flowchart of
FIG. 4 along with each operational explanation view of FIGS. 5 to
7. First, when the operation of supercritical processing apparatus
3 begins, inert gas is supplied into processing space 30 via inert
gas line 45 in a closed state of processing space 30. Further, each
of heaters 322, 314, and 452 is turned ON and the temperature of
upper chamber 31 and disposition board 321 is adjusted to, for
example, 100.degree. C., based on a temperature detection result
detected from a temperature detector (not shown), and then waits
for a next operation (step S101 of FIG. 5A).
[0107] By supplying the inert gas to processing space 30 in the
closed state, oxygen and moisture existing within processing space
30 are removed, and by heating upper chamber 31 or disposition
board 321, moisture absorbed to upper chamber 31 or disposition
board 321 is separated, so that the atmosphere, in which the
ingredient to facilitating the pyrolysis of HFE within processing
space 30 is removed, is formed. Further, each of FIGS. 5 to 7 omits
the description of inert gas supply chamber 39, but the inert gas
is supplied from inert gas supply chamber 39 through gas supply
hole 391, so that the down flow of the inert gas is always formed
within case 38.
[0108] Wafer W, after completing the liquid processing in cleaning
apparatus 2 and then coated with HFE, is loaded into supercritical
processing apparatus 3 in a standby state through a
loading/unloading port 382 installed in a side surface of case 38.
Supercritical processing apparatus 3, as illustrated in FIG. 5B,
moves bottom plate 32 up to the lower transfer position, interrupts
blocking valve 421, and stops the supply of the inert gas from
inert gas line 45 (step S102). At this time, supporting member 331
of supporting mechanism 33 descends in accordance with the movement
of bottom plate 32, and lifter 361 is operated such that the upper
surface of wafer holding unit 363 is positioned under a carrying
route of wafer W. Further, in FIGS. 5A to 6B, only one pair of
supporting mechanism 33 and one pair of guide member 34 are
illustrated for convenience of the description.
[0109] When wafer W disposed on a carrying arm 82 of the outside
carrying apparatus is loaded into supercritical processing
apparatus 3, and the center part of wafer W reaches the upper side
of lifter 361, lifter 361 ascends to cross with carrying arm 82,
and carrying arm 82 is discharged to an outside of case 38 while
wafer W is held on wafer holding unit 363, as illustrated in FIG.
6A (step S103). Further, as illustrated in FIG. 6B, bottom plate 32
ascends while being guided by guide member 34, and wafer holding
unit 363 of lifter 361 is stored within the concave portion of
disposition board 321. Wafer W is then arranged on disposition
board 321, and received within processing space 30 by combining
disposition board 321 with the to opening portion of upper chamber
31 (step S104). At this time, supporting member 331 of supporting
mechanism 33 ascends in accordance with the movement of bottom
plate 32, so as to support and fix the bottom surface of bottom
plate 32.
[0110] Even when the supply of the inert gas into processing space
30 is interrupted and wafer W is loaded into processing space 30 by
opening processing space 30 as described above, the down flow of
the inert gas is formed within case 38, so that oxygen or moisture
rarely enters into processing space 30 from case 38 and a state is
maintained in which the ingredient facilitating the pyrolysis of
HFE within processing space 30 is removed. The interruption of the
supply of the inert gas from inert gas line 45 when loading wafer W
is for the purpose of directly spraying the heated inert gas to
wafer W and preventing HFE coated on the surface of wafer W from
being dried. However, the timing for supply and interruption of the
inert gas to processing space 30 can be variously changed as
described later.
[0111] Further, as illustrated in FIG. 7A, switching valve 422 is
switched to HFE supply line 42, and blocking valves 421 and 441 of
HFE supply channel 311 and discharge channel 313 are switched to
"OPEN" (indicated as "O" in FIG. 7A), the supply of HFE from HFE
supply channel 311 to processing space 30 begins, and the
atmosphere within processing space 30 is discharged to discharge
channel 313, so that the atmosphere within processing space 30 is
substituted with HFE (step S105).
[0112] When a predetermined amount(e.g., about 80% of the volume of
processing space 30) of HFE is supplied to processing space 30,
blocking valves 421, 431, and 441 of HFE supply channel 311, HFE
discharge channel 312, and discharge channel 313 are shifted to
"STOP" (indicated as "S" in FIG. 7B), so as to seal processing
space 30 (step S106). Then, when the output of heater 322 of bottom
plate to 32 increases such that the temperature within processing
space 30 becomes, for example, 200.degree. C., HFE is heated within
sealed processing space 30 and expanded, so that the pressure of
the inside of processing space 30 is raised up to, for example, 3
MPa, finally resulting in the supercritical state of HFE (FIG. 7C,
step S107).
[0113] In accordance with the achievement of the supercritical
state of HFE, the supercritical processing in which the liquid on
the surface of wafer W is changed to a supercritical fluid state
and a supercritical process is performed to dry wafer W. In the
state change to the supercritical fluid from the liquid, an
interface is not formed between the liquid and the supercritical
fluid, so that the capillary force is not applied to pattern 11 on
wafer W, thereby drying wafer W without the generation of the
pattern collapse. Further, as the dissolved oxygen is removed by
the bubbling, HFE itself has a high thermo-stability, and oxygen or
moisture rarely exists in processing space 30 as described above,
and HFE used in the supercritical processing is in a state in which
the facilitation of the pyrolysis of HFE is difficult, so that the
fluorine atoms are rarely discharged from HFE during the
supercritical processing. Therefore, it is possible to dry wafer W
while preventing a film, such as SiO.sub.2 film 12, formed on the
surface of wafer W from being etched or the fluorine atoms from
being injected into the semiconductor device, such as wafer W or
pattern 11.
[0114] Then, after a predetermined time elapses, as illustrated in
FIG. 7D, blocking valve 431 of HFE discharge channel 312 is
switched to "OPEN" so that HFE is discharged from processing space
30 (step S108). HFE discharged to HFE collection line 43 is cooled
in cooling unit 432 and collected in HFE supply unit 4. Through the
operation, the processing space 30 is depressurized, and when the
inside pressure is approximately identical to air pressure,
blocking valve 431 of HFE discharge channel 312 is switched to
"STOP". Further, blocking valves 421 and 441 of HFE supply channel
311 and discharge channel 313 are switched to "OPEN" as illustrated
in FIG. 7E, and switching valve 422 is switched, so that the supply
of the inert gas from inert gas line 45 begins(step S109). HFE left
within processing space 30 is collected in gas collection unit 442
installed at discharge line 44.
[0115] Next, bottom plate 32 descends, processing space 30 is
opened, and then wafer W is unloaded from supercritical processing
apparatus 3 in a route contrary to that in loading in wafer W,
completing a series of operations (step S110). Then, when wafer W
is unloaded, bottom plate 32 ascends and processing space 30 is
closed. Then, the output of each heater 322 is adjusted such that
the temperature of upper chamber 31 and disposition board 321
becomes 100.degree. C., and supercritical processing apparatus 3
waits for loading of next wafer W (step S101).
[0116] Supercritical processing apparatus 3 according to the
present embodiment has following effects. The supercritical
processing is performed under the condition where the pyrolysis of
HFE is difficult by removing the ingredient that facilitates the
pyrolysis of HFE from the processing chamber (upper chamber 31 and
bottom plate 32) before the supercritical processing begins,
removing the dissolved oxygen within HFE, and using HFE having a
property that the pyrolysis of HFE is difficult. Therefore, the
generation of the pattern collapse of pattern 11 formed on the
surface of wafer W and the injection of the fluorine atoms
constituting HFE into wafer W are suppressed, thereby achieving a
high-quality processing result.
[0117] If at least one or more of the pyrolysis ingredient removing
units of aforementioned (A) to (C) is included, it is possible
obtain the effect of the present disclosure in accordance with a
removal capability of the ingredient facilitating the to pyrolysis
of HFE by the pyrolysis ingredient removing unit. However,
especially, it is effective to decrease the dissolved oxygen within
HFE by the pyrolysis ingredient removing unit according to the
construction (A), and to remove oxygen or moisture within
processing space 30 by the pyrolysis ingredient removing unit
according to the construction (B) as described above.
[0118] Here, in the description of the operation with reference to
FIGS. 4 to 7, as schematically illustrated in FIG. 8A, there is
described the example in which HFE is discharged to HFE collection
line 43 from processing space 30 and the inside pressure is
decreased. Then, the inert gas is supplied to processing space 30
during the time frame before a following wafer W is loaded, thereby
forming the atmosphere in which the ingredient of the pyrolysis of
HFE within processing space 30 is removed. However, the time for
supply of the inert gas is not limited thereto. In FIGS. 8A, 8B,
9A, and 9B to be described below, the uppermost row represents the
change of the atmosphere within processing space 30 in the
rightward direction along the time axis, and the second column
represents the atmosphere of case 38. The lower side of the two
columns represent an open/closed state (a state in which bottom
plate 32 descends is referred to as "OPEN", and a state, in which
bottom plate 32 ascends and processing space 30 is sealed, is
referred to as "CLOSE") of processing space 30 corresponding to
each timing, and an open/closed state of each of blocking valves
421, 441, and 431 of a switching position of switching valve 422 in
the side of HFE supply channel 311, the side of HFE supply channel
311, the side of discharge line 44 (discharge channel 313), and the
side of the HFE collection line (HFE discharge channel 312).
[0119] For example, as illustrated in FIG. 8B, it is acceptable to
supply the inert gas to processing space 30 only during the loading
and unloading operation of wafer W. In the example illustrated in
FIG. 8B, processing space 30 opened for unloading wafer W maintains
its opened state until following wafer W is loaded. However, for
example, processing space 30 may be closed after unloading wafer W
and supply the inert gas to processing space 30 only for a time
period while wafer W is loaded during which processing space 30 is
opened, so as to prevent the entrance of oxygen or moisture from
the outside. In each of FIGS. 8B, 9A, and 9B, the indication of a
column representing the atmosphere within case 38 is omitted.
However, similar to a case of FIG. 8A, it is acceptable to form the
down flow of the inert gas within case 38. Further, when the
atmosphere within processing space 30 is substituted by the inert
gas after wafer W is loaded as in the present example, the quantity
of used nitrogen gas may be reduced by removing only the moisture
from the down flow formed within case 28 by a dry air having a dew
point of, for example, -50.degree. C. or lower. Alternatively, the
atmosphere within case 38 may be replaced by a typical
atmosphere.
[0120] Further, as illustrated in FIG. 9A, processing space 30 may
be closed after wafer W is loaded, and then, HFE may be supplied
after a sufficient amount of inert gas is supplied for a short time
period for discharging oxygen or moisture existing within
processing space 30. As such, if the conditions that (1) the
ingredient facilitating the pyrolysis of HFE has been removed from
processing space 30 before the introduction of HFE begins, and (2)
HFE on the surface of wafer W is not dried before the start of the
introduction of HFE, are satisfied, it is possible to obtain the
effect of the present disclosure.
[0121] Therefore, as illustrated in FIG. 9B, the inert gas may be
continuously supplied to processing space 30 for a time period
after discharging HFE within processing space 30 before the start
of supplying HFE for a next processing. When the to down flow of
the inert gas is formed in the side of case 38, the above
continuous supply of the inert gas is more effective because the
inert gas is introduced into processing space 30 from case 38 while
processing space 30 is opened and wafer W is loaded.
[0122] Further, with respect to a time for heating upper chamber 31
and disposition board 321 by each of heaters 322, 314, and 452,
similar to the supply time of the inert gas, if the conditions that
(1) processing space 30 is sealed after the completion of the
loading of wafer W and the ingredient facilitating the pyrolysis of
HFE has been removed in processing pace 30 before the start of the
introduction of HFE and (2) HFE on the surface of wafer W is not
dried before the start of the introduction of HFE, are satisfied,
it is possible to obtain the effect of the present disclosure.
[0123] At this time, in order to prevent the moisture separated
from upper chamber 31 and disposition board 321 from staying within
processing space 30, a purge gas supply unit may be installed for
passing purge gas through the inside of processing space 30, either
simultaneously with or after heating upper chamber 31 and
disposition board 321, and the separated moisture may be discharged
by the purge gas. While the purge gas used for discharging the
moisture may have a low moisture content, other gas of which the
dew point is adjusted by -50.degree. C. or less, may be used as
well.
[0124] In addition, the supply of the inert gas to the processing
chamber (upper chamber 31 and bottom plate 32) is not limited to a
case in which processing space 30 is closed. For example, the inert
gas may be supplied in a state where bottom plate 32 descends, and
processing space 30 is opened. In order to form the atmosphere in
which the ingredient facilitating the pyrolysis of HFE within
processing space 30 is removed, supercritical processing apparatus
3 is not limited to a case in which all of the constructions, for
supplying the inert gas to processing space 30, heating upper
chamber to 31 and disposition board 321, and supplying the inert
gas from inert gas supply chamber 39 to case 38, are included
serving as a dry atmosphere forming unit. The dry atmosphere may be
formed by using only one construction or a combination of two
constructions among the constructions.
[0125] In the aforementioned various embodiments, while HFE is
adopted as the processing liquid that includes the fluorine
compound for the supercritical processing for wafer W, the
processing liquid adoptable in the present disclosure is not
limited to HFE. For example, HFC can be used as the processing
liquid including the fluorine compound. In this case, by using
supercritical processing apparatus 3 including the pyrolysis
ingredient removing unit for (A) decreasing the dissolved oxygen
within HFC, (B) removing oxygen or moisture within processing space
30 in which the supercritical processing is performed, and (C)
suppressing the moisture absorption to the wall surface of the
processing chamber, it is also possible to dry wafer W while
suppressing the pyrolysis of HFC to suppress the introduction of
the fluorine atoms into wafer W.
EXAMPLARY EMBODIMENTS
[0126] (Experiment 1) The pyrolysis property of HFE was
investigated under the existence of activated carbon used in gas
collection unit 442.
[0127] A. Experimental Condition
Embodiment 1-1
[0128]
CF.sub.3CH.sub.2OCF.sub.2CHF.sub.2(1,1,2,2-tetrafluoro-1-(2,2,2-tri-
fluoroethoxy)ethane) illustrated in FIG. 10A was heated for 72
hours in the presence of the activated carbon, and under conditions
of 120.degree. C. and an atmospheric pressure. And, the
concentration of fluorine ions emitted from HFE and the
concentration of acid contents were measured.
Embodiment 1-2
[0129]
CF.sub.3CH.sub.2OCF.sub.2CHFCF.sub.3(1,1,2,3,3,3-hexafluoro-1-(2,2,-
2-trifluoroethoxy)propane) illustrated in FIG. 10B was heated with
the identical condition to (Embodiment 1-1), and the concentration
of fluorine ions and the concentration of acid contents were
measured.
Embodiment 1-3
[0130]
CF.sub.3CHFCF.sub.2OCH.sub.2CF.sub.2CF.sub.3(2,2,3,3,3-pentafluoro--
1-(1,1,2,3,3,3-hexafluoropropoxy)propane) illustrated in FIG. 10C
was heated with the identical condition to (Embodiment 1-1), and
the concentration of fluorine ions and the concentration of acid
contents were measured.
Comparative Example 1-1
[0131]
(CF.sub.3).sub.2CFCF.sub.2OCH.sub.3(1,1,2,3,3,3-hexafluoro-1-methox-
y-2-trifluoromethylpropane) illustrated in FIG. 11A was heated with
the identical condition to (Embodiment 1-1), and the concentration
of fluorine ions and the concentration of acid contents were
measured.
Comparative Example 1-2
[0132]
(CF.sub.3).sub.2CFCF.sub.2OCH.sub.2CH.sub.3(1,1,2,3,3,3-hexafluoro--
1-ethoxy-2-trifluoromethylpropane) illustrated in FIG. 11B was
heated with the identical condition to (Embodiment 1-1), and the
concentration of fluorine ions and the concentration of acid
contents were measured.
Comparative Example 1-3
[0133]
(CF.sub.3).sub.2CFCF(OCH.sub.3)CF.sub.2CF.sub.3(1,1,1,2,3,4,4,5,5,5-
-decafluoro-2-trifluoromethyl-3-methoxypentane) illustrated in FIG.
11C was heated with the identical condition to (Embodiment 1-1),
and the concentration of fluorine ions and the concentration of
acid contents were measured.
[0134] B. Experimental Result
[0135] Even if HFE in each of (Embodiment 1-1) to (Embodiment 1-3)
was subjected to the heating processing under the existence of the
activated carbon, the fluorine ion and the acid content were equal
to or less than a detection limit (0.02 ppm of fluorine ion, 1 ppm
of acid content). In the meantime, in (Comparative example 1-1),
the measured concentration of fluorine ions and the measured acid
content were 45 ppm and 160 ppm, respectively, and also in
(Comparative example 1-2) and (Comparative example 1-3), the
measured concentration of fluorine and the measured acid content
were similar to those of (Comparative example 1-1). Therefore, it
appears that, under the existence of the activated carbon, HFE
according to each of the embodiments had a high thermo-stability,
and HFE according to the comparative examples had a low
thermo-stability as compared to HFE according to the
embodiments.
[0136] (Experiment 2) The supercritical processing were performed
for removing the liquid after the liquid processing from wafer W on
which various patterns 11 by using HFE according to (Embodiment
1-1), and the generation of the pattern collapse was
identified.
A. Experimental Condition
Embodiment 2-1
[0137] The supercritical processing was performed on wafer W
including a silicon oxide film, on which the MEMS having a
cantilever structure was formed, after the liquid processing of
wafer W.
Embodiment 2-2
[0138] The supercritical processing was performed on wafer W in
which fine pattern 11 was formed on a silicon oxide film, after the
liquid processing.
Embodiment 2-3
[0139] The supercritical processing was performed on wafer W in
which pattern 11 was formed on a porous silicon oxide film having
fine holes, after the liquid processing.
B. Experimental Result
[0140] As a result of expansive investigation of wafer W in each of
(Embodiment 2-1) to (Embodiment 2-3), it could be identified that
the supercritical processing was being performed without the
generation of the pattern collapse or the damage of the fine holes
to of the porous oxide film.
[0141] From the foregoing, it will be appreciated that various
embodiments of the present disclosure have been described herein
for purposes of illustration, and that various modifications may be
made without departing from the scope and spirit of the present
disclosure. Accordingly, the various embodiments disclosed herein
are not intended to be limiting, with the true scope and spirit
being indicated by the following claims.
* * * * *